A digital camera has a configuration where a picked-up photographed image is converted to image data of a digital signal by use of an imaging device such as an image sensor, and the data is recorded in a recording medium such as a built-in memory or a memory card. Further, among digital cameras, there is a lens interchangeable digital camera called a single-lens digital camera, with such a configuration where a variety of lenses are interchangeable according to user's preferences.
In this lens interchangeable digital camera, since a lens is arranged in a central section of a cylindrical lens barrel of an interchangeable lens unit, an electronic circuit device for controlling movement of the lens and the like has a structure of being mounted on a circuit board in a ring shape or in a shape like a partially missing ring shape.
As thus described, in the lens interchangeable digital camera, although the electronic circuit device mounted on the ring-shaped circuit board is installed in the cylindrical lens barrel of the interchangeable lens unit, since the circuit board is formed in the ring shape and thus has a small area, it is difficult to expand an area of a ground pattern of the circuit board. As a result, a ground potential of the electronic circuit device becomes unstable, thereby causing a problem of an influence exerted by an unwanted radiation noise from the electronic circuit device.
In recent years, a lens interchangeable digital camera capable of photographing high-definition moving pictures has attracted much attention. In order for the digital camera to be capable of photographing high-definition moving pictures, it is necessary to increase the number of times of autofocus operations per unit time, which leads to a higher speed of a digital signal, namely a higher cyclic frequency of the signal, the digital signal flowing through the circuit board of the electronic circuit device installed in the interchangeable lens unit. As a result, the influence exerted by the unwanted radiation noise becomes more problematic.
Meanwhile, as described in Patent Document 1, there is known a configuration where in an interchangeable lens unit, a printed board mounted with a CCD drive circuit is screwed to a lens barrel so as to be grounded thereon, thereby suppressing generation of unwanted radiation due to a clock signal generated from the CCD drive circuit.